Screw conveyers, augers and the like typically incorporate or comprise a screw member for propelling particulate, granular or other free flowing material along the length of a barrel in an axial direction as determined by the rotation of the screw. The propulsion of the material is achieved by the successive turns of a continuous helical (spiral) blade (known in the art as flighting) secured to and radiating from a central driving shaft or barrel which is arranged for rotation by an appropriate power source (manual or otherwise).
In the case of a screw conveyor, the material being propelled by the successive turns of the flighting is confined to the spaces between successive turns by a casing which encloses and cooperates with the outer periphery of the flighting. Though in some cases the screw member is of integral form, in most cases and for a variety of reasons, it is customary to form the flighting separately and independently of the barrel. The flighting typically consists of a helicoid (helical rolled from a flat steel bar) flighting welded directly to the barrel. It will be appreciated that it is found in practice, that the flight wears due to the friction of the material being axially propelled by the flighting thereby requiring replacement of either the flighting or the entire screw. It will also be appreciated that the flighting and the barrel are typically made from similar materials because of the problems otherwise presented by different coefficients of expansion of dissimilar materials.
When replacement of flighting is required, the flighting is typically removed by flame cutting the flighting flush with the barrel. The barrel is then ground smooth prior to attaching new flighting. The new flighting is then carefully tacked to the barrel in a helical pattern by welding. It will be appreciated that this procedure is a very time consuming and labor intensive procedure.
It will be appreciated from the foregoing that there is a significant need for a new screw design that overcomes the problems of the prior art. In particular, what is needed a is screw design that incorporates a flighting design that allows for rapid and economical flighting replacement. It is an object of the present invention to provide a field replaceable helical flight for use on a screw conveyor, auger or like transporting, conveying and propelling devices. It is another object of the present invention to provide a screw having a field replaceable helical flight for use in a rotary hearth furnace subjected to temperatures required for lime calcination or iron-ore reduction. Yet another object of the present invention is to provide a helical flight of a screw that may be quickly replaced. Another object of the present invention is to provide a screw having a field replaceable flight and a method of replacing the helical flight that is simple and economical.